A fuel cell is constructed from an MEA (Membrane-Electrode Assembly) and separators sandwiching the MEA. A gas diffusion layer is disposed between the MEA and the separator. In the separator, at a power generating region, a fuel gas passage or an oxidant gas passage is formed at a surface of the separator facing the MEA, and a coolant passage is formed at a surface opposite the surface facing the MEA. Further, in the separator, at a non-power generating region located at an outer portion of the separator, a fuel gas manifold, an oxidant gas manifold and a coolant manifold are formed. The fuel gas passage communicates with the fuel gas manifold via a fuel gas inlet/outlet passage, and the oxidant gas passage communicates with the oxidant gas manifold via an oxidant gas inlet/outlet passage. The gas inlet/outlet passage includes a gas passage groove formed at a bottom surface of the gas inlet/outlet passage and a sealing plate disposed at the gas inlet/outlet passage and covers the gas passage groove.
As disclosed in Japanese Patent Publication 2001-110436, the sealing plate is constructed of a stepped plate in order to prevent interference with the diffusion layer.